The relative abundance (%) of planktonic foraminifera over time in core MD032607, located off the coast South Australia

The advent of deep-sea drilling in the 1950's prompted the use of planktonic foraminifera (unicellular protozans) as palaeoceanographic indicators. They provide a natural archive of past environmental changes due to their global distribution, their prolific productivity and sensitivity to environmental variations.The highest species abundance of foraminifera in core MD032607 was recorded by Globigerina bulloides (~45%) during the penultimate glacial period (MIS 6) and, generally, was the most abundant with an average abundance of 19.5%. The dominance of the sub-polar, transitional species, Ga. bulloides in this core suggests the influence of cold, nutrient-rich water during certain isotopic stages. Conversely, the dominant warm and oligotrophic species Globigerinoides ruber recorded its lowest abundance in Marine Isotope Stage (MIS) 6, and is totally removed from the record (0%) at 146K, 142K, and 139K yrs BP.

20世纪50年代深海钻探技术的问世，推动了浮游有孔虫（planktonic foraminifera，单细胞原生动物）作为古海洋学指标的应用。该类生物因全球分布广泛、种群生产力旺盛且对环境变化敏感度高，成为记录古环境变迁的天然档案载体。在MD032607岩芯（core MD032607）中，有孔虫的物种丰度峰值出现在倒数第二次冰期（MIS 6），由泡抱球虫（Globigerina bulloides）贡献约45%的丰度；该物种整体为该岩芯中丰度最高的类群，平均占比达19.5%。该岩芯中亚极地过渡型物种泡抱球虫占据优势，表明在部分同位素阶段存在寒冷富营养水体的影响。与之相对，占主导的暖水贫营养物种红拟抱球虫（Globigerinoides ruber）在海洋同位素阶段6（MIS 6）时丰度达到最低值，并在距今14.6万、14.2万及13.9万年的层位中完全消失，丰度为0%。